ALMATY, Kazakhstan -- Kazakhstan's upper house of parliament approved a bill Thursday that backers say will help combat religious extremism, but that critics call a blow to freedom of belief in the ex-Soviet nation.

The bill approved by the Senate will require existing religious organizations in the mainly Muslim nation to dissolve and register again through a procedure that is virtually guaranteed to exclude smaller groups, including minority Christian communities.

Passage of the bill marks a reversal of authoritarian President Nursultan Nazarbayev's earlier attempts to cast Kazakhstan as a land of religious tolerance. One activist estimates that two-thirds of existing religious groups could be abolished as a result of the new law.

Backers of the revised law argue that the legislation is necessary to fight extremism. Authorities have been unsettled by an uncharacteristic outburst of Islamist-inspired violence in the oil-rich western regions over the summer.

"The bill prohibits religious associations that are bent on the destruction of families, force the abandonment of property in favor of religious communities ... and that are harmful to the morals and health of citizens," the Senate said this week in a statement.

Most Muslims in Kazakhstan adhere to a largely liberal strand of the faith, although more extreme devotees are reportedly growing in number. Overall mosque attendance is on the rise and the government is seemingly intent on carefully vetting the creeping rise of religious fervor.

Many are skeptical, however, that regulating faith groups will have any success in stemming the tide of extremist underground Islamist movements.

The bill needs approval from Nazarbayev before it can become law – a mere formality since he urged parliament earlier this month to introduce tighter controls over religious groups.

Critics are angered by the speed with which the bill has been rushed through Parliament and say there has been a lack of public debate over the legislation.

The law will require groups to reach membership number thresholds before they can register at various levels.

To register locally, a group must have 50 members. To register at a regional level, they require 500 members. The most complicated procedure will be registering nationwide, which requires a group to have 5,000 members across all the country's regions.

"Several minority religious groups do not have the required number of members and would be prohibited from continuing their activities and subject to fines if they disobey," the Washington-based democracy watchdog Freedom House said in a statement prior to the Senate vote.

Other provisions envision strict oversight of missionary activity, government reviews on religious literature and texts, and rules on where people are permitted to pray.

Kazakhstan has repeatedly gone through the motions of introducing restrictions on religion during the two decades since it gained independence. Those efforts have been routinely quashed in the final stages amid vocal international criticism.

Although Kazakhstan has attempted to portray itself as a haven for diverse faith organizations, activists say that minority groups consistently face harassment.

"This new law has simply legalized the current practice ... of persecuting unregistered minority religious groups and limiting missionary activity," said rights activist Ninel Fokina, head of the Almaty Helsinki Committee.

Fokina said authorities have been openly speaking about the need for a purge in the religious sphere.

"I believe that out of the 4,500 religious groups currently in existence, barely 1,500 will remain," she said.

Fokina said the new rules would also greatly complicate the life of even relatively large Christian Protestant communities, such as Lutherans, Baptists, Seventh-day Adventists and Jehovah's Witnesses.